A conventional paging radio receiver system includes a paging radio receiver having an EEPROM (electrically erasable programmable ROM) for storing a predetermined specific call number, alarm signal patterns, etc., and an access unit for access to the EEPROM. The radio receiver is provided with a speaker and/or an LED (light emitting diode) for informing a callee (a pager carrier) of a call from a caller. The speaker generates sound information and the LED is turned on and off to provide visual information, respectively, in accordance with one of the stored alarm signal patterns, when a call number of a received signal is equal to the predetermined specific call number of the EEPROM.
According to the conventional paging radio receiver system, the access unit is connected to the radio receiver, so that the stored information is easily read from the EEPROM, and replaced therein by new information. This makes it easy to maintain the paging radio receiver, as compared to a paging radio system using a non-erasable and non-programmable ROM.
However, the conventional paging radio receiver has a disadvantage in that the EEPROM can be accessed by an unauthorized operator. That is, information stored in the EEPROM can be read and new information can be written in the EEPROM easily, respectively, by an unauthorized pager carrier, for instance, if the paging radio receiver system is stolen.